1. Field of the Invention
The present invention relates generally to equipment and apparatus for excavation, and more particularly, but not by way of limitation, to an improved excavation bucket having a resilient portion adapted to temporarily deflect to prevent damage to buried objects such as pipelines, as well as excavation apparatus utilizing the improved excavation bucket, and methods of use and manufacture thereof.
2. Background of the Invention
Various pieces of equipment are well known in the art for ground excavation. For example, backhoes, trackhoes, tractors, and the like have long been provided with articulated arms and excavation buckets for digging and removing earth, such as for installing and/or unearthing pipelines or other buried items that may be in the vicinity of such buried pipelines. Numerous problems exist with excavation equipment previously known in the art.
One area in which problems are especially prevalent is the excavation of earth in the vicinity of previously-buried pipelines that are active or in use, i.e., have fluids flowing or contained within the pipeline. For example, active pipelines may have sensitive fluids therewithin, such as oil, natural gas, or fresh water. Oil and natural gas are especially sensitive in that a puncture in the pipeline may release flammable and/or combustible fluids that may endanger workers and/or property in the vicinity of the pipeline.
Backhoes especially are often used to excavate earth. Backhoes are generally more efficient than hand-digging because they are provided with an articulated arm and bucket actuated by mechanical means, such as hydraulic cylinders, that permits the bucket to impart much greater force than a typical hand shovel. Additionally, the bucket of backhoe is capable of removing a far greater volume of material than a typical hand shovel. However, known backhoes and related excavation equipment, such as excavation buckets, also have a number of drawbacks. For example, the extraordinary force exerted by the bucket of a backhoe can easily damage existing pipelines. Backhoe buckets are typically made of rigid, durable materials such as hardened steel and iron. Such buckets are also typically formed with a sharpened cutting blade and/or a number of pointed cutting teeth to assist in breaking through packed dirt, clay, and rocks. These known buckets impacting, or pressing against, existing pipelines during digging or excavation can deform, puncture, and otherwise damage existing pipelines.
Previously, most pipelines carrying oil, natural gas, and water were generally formed of rigid, durable materials such as steel or iron. Nevertheless, steel and iron pipelines were still vulnerable to damage by steel buckets. U.S. Pat. No. 4,905,386, issued to Taylor on Mar. 6, 1990, is directed to one attempt to prevent damage to steel pipelines: a cutting edge member for fitting onto an excavation apparatus wherein the cutting edge member is of softer material than iron for digging around pipelines. Taylor teaches that the cutting edge member comprises a flat plate structure formed of soft metals which are softer than steel, for example, aluminum, brass, copper, and Monel®. Taylor further teaches that when the cutting edge contacts a steel pipeline, the cutting edge will deform, e.g., bend, but will not damage the pipeline. The patent describes a test of the apparatus in which the cutting edge struck a steel pipeline and the cutting edge was badly bent and deformed, but did not damage the steel pipeline. The deformed cutting edge then had to be replaced before digging could resume.
The Taylor metal cutting edge of the Taylor patent still has a number of drawbacks. The blade must be replaced each time a steel pipeline is struck. Additionally, the blade is attached to a standard steel bucket and when the blade reaches its limit of deformation, the entire force of the steel bucket will bear down on the pipeline and will eventually still damage the pipeline. The Taylor apparatus is therefore dependent on an operator or other individual visually monitoring the blade to detect when it deforms. More modernly, many pipelines are formed of polymeric material, “poly pipe,” that is much less rigid than steel pipe, and is therefore more vulnerable to puncture and damage. Additionally, modern pipelines may be coated with special materials during manufacture or prior to installation, for example cathodic, anodic, and epoxy coatings. Damage to these coatings may render a pipeline vulnerable to corrosion or the like. The blade of the Taylor patent is specifically designed to deform when it contacts a steel pipe, and would likely still easily puncture and/or otherwise damage a modern poly pipe, as well as easily scrape off pipeline coatings.
Several other attempts have been made to prevent damage to buried pipelines. Systems have been proposed to bury a conductive “tracer” wire with a buried pipeline when the pipeline is first installed. When digging or excavation is undertaken near the pipeline, a current can be passed through the tracer wire and a sensor system attached to the bucket to indicate to an operator of the backhoe when the bucket approaches or comes close to the tracer wire, and thus, the pipeline. Such systems require the tracer wire to be placed consistently along the length of the pipeline and requires electronic sensing equipment which requires electrical power and is subject to failure. If the tracer wire is installed with any breaks, or is later broken, the system is rendered inoperable. Additionally, pipelines buried before such systems came into use are not provided with the necessary tracer wire and cannot be sensed by such systems. Such systems, when usable, may also be complex and cost-prohibitive.
To this end, a need exists for more versatile and simpler systems and apparatus for preventing damage to buried pipelines while digging and/or excavating in the vicinity of such pipelines. It is to such a need that the present invention is directed.